If they were "barely visible," how did she happen to see them? It's extremely rare for anyone to look that closely at their poop.
I suggest it's likely she saw bits of food. I would have her poop into a clean disposable sort of container, such as a cottage cheese, sour cream sort of container and look for yourself.
I also doubt they are worms. They usually cause a very uncomfortably itchy rectum. If they are visible, they move around.
If you see something that looks out of place in her poop, make an appointment with the doctor on Monday. If she has other symptoms such as an itchy bottom, digestive difficulties, abdominal pain or weight loss, take her to the doctor even if you don't see anything.
Could your daughter be anxious enough to examine her poop? If so, talk with her about how she's feeling and why she looked through her poop.